package leetcode.editor.cn;
//给定二叉树的根节点 root ，返回所有左叶子之和。 
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// 示例 1： 
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//输入: root = [3,9,20,null,null,15,7] 
//输出: 24 
//解释: 在这个二叉树中，有两个左叶子，分别是 9 和 15，所以返回 24
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// 示例 2: 
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//输入: root = [1]
//输出: 0
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// 提示: 
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// 节点数在 [1, 1000] 范围内 
// -1000 <= Node.val <= 1000 
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// Related Topics 树 深度优先搜索 广度优先搜索 二叉树 👍 674 👎 0


//leetcode submit region begin(Prohibit modification and deletion)

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 * int val;
 * TreeNode left;
 * TreeNode right;
 * TreeNode() {}
 * TreeNode(int val) { this.val = val; }
 * TreeNode(int val, TreeNode left, TreeNode right) {
 * this.val = val;
 * this.left = left;
 * this.right = right;
 * }
 * }
 */
class Solution205 {

    int sum = 0;

    public int sumOfLeftLeaves(TreeNode root) {
        transfer(root, false);
        return sum;
    }

    private void transfer(TreeNode node, boolean isLeft) {
        if (node == null) {
            return;
        }
        if (node.left == null && node.right == null && isLeft) {
            sum += node.val;
            return;
        }
        transfer(node.left, true);
        transfer(node.right, false);

    }

    public class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;

        TreeNode() {
        }

        TreeNode(int val) {
            this.val = val;
        }

        TreeNode(int val, TreeNode left, TreeNode right) {
            this.val = val;
            this.left = left;
            this.right = right;
        }
    }
}
//leetcode submit region end(Prohibit modification and deletion)
